Unification of England

The Unification of England occurred from 878 to 954 AD when the Anglo-Saxon kingdom of Wessex conquered the Viking-ruled Danelaw and annexed the fellow Anglo-Saxon kingdom of Mercia to forge a united "Kingdom of England". In 900 AD, the Kingdom of Wessex had only recently secured its independence from the Viking threat. Over the next half-century, a series of able kings progressively conquered the areas of Viking England, until their lands bordered with Scotland. Now the Wessex rulers' claim to be "Kings of the English" was no hollow boast.

Background
Alfred the Great saved Wessex from conquest by the Vikings, but the Scandinavian invaders still occupied large portions of England's north and the Midlands. The survivors among the Vikings of the Great Heathen Army of 865 AD and the Summer Army of 871 AD had mostly settled down in Mercia, East Anglia, and Northumbria, establishing bases in strongholds at York and the Five Boroughs (Lincoln, Derby, Nottingham, Leicester, and Stamford). The campaigns of Alfred the Great caused some difficulties for the British Vikings. By 900, they were looking to the Viking settlements in Ireland, the Isle of Man, and the Scottish Isles for support and reinforcements. In addition to western Mercia and Wessex, the Vikings faced opposition from what remained of the English kingdom of Northumbria, around Bamburgh.

History
Edward the Elder, the son of King Alfred the Great, hardly had a smooth path to succession. After Alfred's death in 899 AD, Aethelwold, his nephew, attempted to seize the throne. He failed, fleeing to Viking-held Northumbria, where the Scandinavians installed him as their king. Edward spent the next four years trying to defeat Aethelwold, who finally perished at the Battle of the Holme in 903.

Taking Viking territories
Edward launched raids into Danish territories in 909, but it was only during a Viking counter-strike southwards the following year that he won his first significant victory, at Tettenhall, where three Danish kings perished, together with huge numbers of their men. The death in 911 of Aethelred, who had been ealdorman of Mercia, further strengthened the Wessex king's position, as his replacement was his widow Aethelflaed, the "Lady of the Mercians", who just happened to be Edward's sister.

Aethelflaed secured their position in Mercia by fortifying Chester in 907 and then transforming the ancient royal center of Tamowrth into a burh, or defensive fortification, in 913. She created a series of further burhs, including Stafford, Warwick, Eddisbury, and Runcorn. Meanwhile, Edward campaigned to the north and the east, forcing the Viking kingdoms of Essex, Bedfordshire, and Northamptonshire to surrender by 916. The Scandinavians of the Five Boroughs did not present a common front and had not had time to establish a centralized kingship such as grew up in York within a few years. When Aethelflaed captured Derby in 917, the only remaining Viking forces south of the Humber were based in Leicester, Stamford, Nottingham, and Lincoln. By the end of the following year all of these were in Edward's possession, while York itself had submitted to Aethelflaed.

Edward's setbacks
Edward then suffered two setbacks. Firstly, Aethelflaed died, opening up the question of the succession to Mercia at a less-than-convenient moment. Edward had Aethelflaed's daughter, Aelfwynn, seized and removed to Wessex, where she could not provide the focus for any resistance to his rule over Mercia. Potentially more serious was the rise of a new Viking power in the north of England. The weakening of the Danes of the Five Boroughs had opened up opportunties for ambitious adventurers from other viking lands and so in 918, Ragnall ua Imair, the grandson of Ivar the Boneless, desecended on northern England. After an indecisive battle at Corbridge, he moved south and seized York, establishing a Viking kingdom, which acted as a block to Wessex's interests in the region. Edward reacted by constructing a series of fortresses in the north-west and Midlands (including Nottingham) to prevent any further expansion from York. By 920 Ragnall felt it politic to accept Edward as his overlord (joining the Welsh kings of Gwynedd and Dyfed, who had done so in 918). Although this and the submission of Ealdred, Earl of Bamburgh, and the Kings of Strathclyde and Constantine gave Edward notional lordship over virtually all of Britain; he exercised no real control in those areas. By the time of Edward's death in 924, Mercia was fully incorporated into Wessex. Aethelstan, the new king moved to secure the position on his northern border by a marriage alliance between his sister and Sihtric Caech, the Viking ruler of York. When Sihtric died in 927, Aethelstan took the opportunity to drive out his successor, Olaf, and take York for himself, razing its fortifications in an effort to neutralize any possible future threat. In the afterglow of victory, he arranged a meeting at Penrith in which he received the submission of King Constantine II of SCotland, Hywel Dda of Dyfed, the King of Strathclyde, and the Earl of Bamburgh.

King of all Britain
In 934 Aethelstan felt strong enough to invade Scotland, pushing deep into the central part of the country. King Constantine reacted by building an alliance of all those who feared the expansionist power of Wessex: the Scots, the Strathclyde Britons, the Dublin Vikings, and Scandinavians from the Western Isles. The allied army invaded England in 937 and, at Brunanburh (possibly in Cheshire) suffered a catastrophic defeat in which five kings of the anti-Wessex alliance died (though Constantine himself escaed). Aethelstan now referred to himself as Imperator Orbis Britanniae (emperor of the whole world of Britain), but his death in 939 showed that the paramount position of Wessex was far from secure. Aethelstan's brother Edmund succeeded to the throne of Wessex, but almost at once lost most of the gains of the preceding 30 years, as Olaf Guthfrithson rode the die of a Northumbrian revolt to become Viking king of York, seizing, in addition, most of the land of the Five Boroughs. It took until 942 for Edmund to recover this ground, at which point York itself fell prey to factional infighting, resulting in a rapid succession of kings in no position to reassert themselves against the armies of Wessex. Even so, Edmund was forced to grant Cumbria to Malcolm I of Scotland in exchange for his support against the Vikings.

Final defeat at York
A final threat from York emerged in 947, when Eric Bloodaxe, son of King Harald Fairhair of Norway, and a refugee from Scandinavia, was recognized as king. Six years of confused campaigning followed before Eadred - Edmund' brother and successor as King of Wessex - invaded Northumbria. The citizens of York, seeing the cause was lost, expelled Eric, who was murdered while fleeing northwards. After half a century of warfare, the kings of Wessex had finally, or so they thought, rid England of the threat of Viking conquest, and had emerged as undisputed rulers of all England.

Aftermath
After the fall of York in 947 AD, England experienced more than 30 years of peace in which the strengthening of royal administration and monastic reform were the main developments. Edgar was Eadred's younger son and became King of Wessex in 959. His reign was largely peaceful and in 973 he received the submission of six kings (including those of Scotland, Strathclyde, and Gwynedd), who are said to have taken oars and rowed him ont he River Dee. He supported a series of Church reforms undertaken by his Archbishop of Canterbury, Dunstan, and improved the coinage by insisting that all coins be recalled for reminting every six years. During his reign the custom of appointing ealdormen to larger areas (such as the whole of East Anglia) rather than individual shires became established. The Vikings remained in control of Dublin, the Isle of Man, and parts of Scotland. At the end of the 10th century, new Viking leaders with the resources of whole kingdoms behind them launched fresh raids. Men such as Sweyn Forkbeard of Sweden commenced a new Viking Age in Britain in the 990s.